Heterosubstituierte Acetylene, XXX. Ein neuer Mechanismus der nucleophilen Halogensubstitution an Acetylendreifachbindungen

Abstract

auRer Fluor) mit anschliefiender Onium-Umlagerung2j und Halogen-Anion-cc-Eliminierung wird als neuer Mechanismus der nucleophilen Halogetisubstitution an der Acetylendreifachbindung vorgeschlagezl. Als Beispiel fur diese Reaktionsschritte werden die Umsetzungen von Chlor-tert.-butyl-acctylen (1) mit Phenolat und mit Thiophenolat beschrieben. Directioypezifisch entstehen die @-Addukte 2,s und 6. Thermisch und photochemisch bildet sich aus 5 und 6 das thermodynainisch stabilere Isomere 8, in welchem Chlor und der Thioatherrest unter Vertauschung der C-Atome gewandert sind. Alle Thioather-Isomeren liefern bei der HC1-Abspaltung den tert.-Butylathinyl-thioather 10.Heterosubstituted Acetylenes, XXX 1, A new Mechanism of Nucleophilic Halogen Substitution at Acetylene Triple BondsThe combination of nucleophilic and directiospecific addition in P-position to halogen') (except fluorine) with subsequent onium rearrangement is proposed as a new mechanism of nucleophilic halogen substitution at the acetylene triple bond. The reactions of chloro-rertbutyl-acetylene (1) with phenolate and thiophenolate are described as examples. The padducts 2, 5 und 6 are formed directioqpccifically 5 and 6 give rise photochemically and thermally to the thermodynamically more stable isomer 8 in which the chlorine atom and the thioether residue have migrated and changed their C-atoms All thioether isomers produce the teut-butylethinyl-thioether 10 upon elimination of HCL.

Introduction and extension of ethynyl group using 1,1-dichloro-2,2-difluoroethylene. A convenient route to lithium acetylides and derived acetylenic compounds

“…18•19 The above results also indicate that 1 is a good source of 12, previously obtained from l-chloro-2,2-difluoroethylene with N,Ndipropyllithium amide. 20 The exact fate of CF2=CClLi (12) in the presence of excess 1 is not known, though the final product, an undistillable, dark-colored substance, is thought to have the structure -(CF=CC1)"-. In the presence of excess butyllithium, however, 12 was found to be converted into 1-hexynyllithium (17) after an exothermic reaction.…”

“…Steam distillation of the residual oil (7.3 g) afforded 3.46 g (40.84, 52%) of 9k, mp 39-41 °C. The compound, upon standing in the absence of solvent, had a tendency to be converted into fiberlike crystals: mp 42-43 °C; mass spectrum m/e (rel intensity) 159 (M+, 100), 108 (19), 70 (20); ir (KBr) 3420 (=CH), 2105 cm-1 (C=C).…”

A new mechanism of nucleophilic vinylic substitution and unexpected products in the reaction of chlorotrifluoroethylene with [Re(CO)5]Na and [CpFe(CO)2]K

“…In fact b-additiona-elimination -1,2-shift sequence was among the first mechanisms to be considered for the NS in acetylenes as early as 1970s [20]. Later, it was proposed for vinylic systems to account for the substitution of a leaving group attached to the same carbon atom as the EWG-group [21], and was proved kinetically for the substitution with thiolates anions in a-bromovinylsulphones [22].…”

1,2-Shift of Element-Centered Groups (RnE) in Carbenoid Anions [RnECF2CFCl]−and its Relevance for Nucleophilic Vinylic Substitution: a DFT Study

“…This second step is analogous to FBW rearrangement, with the only difference of migrating group being not the substituent initially present in the molecule, but the entering nucleophile. Such β ‐addition — 1,2‐shift sequence was among the first mechanisms to be considered for the nucleophilic substitution in acetylenes as early as the 1970 s . It was also proposed for the reactions of thiolates (and other soft nucleophiles) with 1,1‐diphenyl‐2,2‐dinitroethylene and α‐halovinylsulphones .…”